Power consumption is an increasingly substantial part of the cost of computer ownership. Improvements in circuit efficiency are far outweighed by increases in circuit density—e.g., the move to multi-core processors. In large multi-server installations, power requirements can run up against limits on the ability of utility companies to deliver needed electricity, and limits on the capability of cooling systems to remove heat dissipated as power is consumed.
Workload management is one approach to limiting power consumption. Many computer components are designed with multiple performance levels so that workloads can be handled at a lower performance level to save power. While this approach is valuable even when the amount of power consumed and saved is not known, more intelligent tradeoffs between performance and power consumption would be achievable where power consumption is known.
Power measurements are typically achieved using a current-sense resistor or an e-fuse to measure DC power consumption with each computer. This approach can be expensive, requiring a precision resistor and/or other power electronics. Inherently, there is some loss of power and some heat generated due to the power drop across the resistor or power electronics. Also, the power electronics may represent an additional point of failure that could impact reliability. In addition, a measurement of DC power consumption does not necessarily correspond precisely to AC power consumption, which most closely corresponds to the costs charged by an electric utility. Accordingly, an economical yet more effective approach of measuring AC power consumption by a computer is needed.
Herein, related art is described to facilitate understanding of the invention. Related art labeled “prior art” is admitted prior art; related art not labeled “prior art” is not admitted prior art.